Identification of growth-hormone- and prolactin-containing neurons within the avian brain

Prolactin (PRL)- and growth-hormone (GH)containing perikarya and fibers ind ependent of the anterior pituitary gland have been reported to exist in the central nervous system of several mammalian species. The specific distribu tions of PRL- or GH-like neurons in the avian forebrain and midbrain, howev er, have not been reported. The objective of the study was to identify GH- and PRL-containing neurons in the hypothalamus and a few extrahypothalamic areas of two avian species. Brain and peripheral blood samples were collect ed from laying and broody turkey hens and ring doves. Broody turkey hens an d doves had significantly higher plasma PRL concentrations compared with la ying hens. Coronal brain sections were prepared and immunostained using ant i-turkey GH and anti-chicken synthetic PRL antibodies. In turkey hens, the most dense GH-immunoreactive (ir) perikarya and fibers were found in hippoc ampus (Hp), periventricular hypothalamic nucleus, paraventricular nucleus, inferior hypothalamic nucleus, infundibular hypothalamic nucleus, medial an d lateral septal area, and external zone of the median eminence (ME). In th e ring dove, a similar pattern of distribution of GH-ir neurons was noticed at the brain sites listed above except that GH-ir fibers and granules were found only in the internal zone of ME and not in the external zone. In bot h turkeys and doves, the most immunoreactive PRL-ir perikarya and fibers we re found in the medial and lateral septal area, Hp (turkey only), and bed n ucleus of the stria terminalis pars magnocellularis. There were no appal-en t differences in the staining pattern of GH- or PRL-ir neurons between the laying and broody states in either species. However, the presence of GH-ir- and PRL-ir perikarya and fibers in several hypothalamic nuclei indicates t hat GH and PRL may influence parental behavior, food intake, autonomic nerv ous system function, and/or reproduction.